Double internal gear wheel pump

ABSTRACT

A double internal gear wheel pump includes two internal gear wheel pumps configured as hydraulic pumps of a hydraulic, slip-controlled vehicle braking system. The double internal gear wheel pump further includes a partition wall that is arranged between both internal gear wheel pumps. The partition wall is configured as a single-piece component of a pump housing, preferably formed by a hydraulic block of the vehicle braking system.

The invention relates to a double internal gear wheel pump comprising two internal gear wheel pumps having the features in the preamble of claim 1. The double internal gear wheel pump is provided for a slip-controlled (ABS, ASR, ESP, FDR) hydraulic vehicle brake system, wherein each of the two internal gear wheel pumps is provided for one brake circuit. Such pumps in slip-controlled hydraulic vehicle brake systems are also referred to as return pumps, wherein piston pumps, rather than gear wheel pumps, may be regarded as conventional.

PRIOR ART

A double internal gear wheel pump of this kind is known from German Offenlegungsschrift DE 10 2007 054 808 A1. It has two internal gear wheel pumps having a common pump shaft for joint driving by means of an electric motor. Pinions of the two internal gear wheel pumps are arranged coaxially adjacent to one another, with an axial spacing, for conjoint rotation on the pump shaft, the gear wheels arranged on the pump shaft being referred to as pinions. Ring gears (gear wheels with internal toothing) of the two internal gear wheel pumps are arranged eccentrically with respect to the pinions and the pump shaft and mesh with the pinions at one point on the circumference or in a region of the circumference. The known double internal gear wheel pump has a multi-part pump casing comprising two cup-shaped cylindrical casing halves, which are assembled axially. Each casing half accommodates one of the two internal gear wheel pumps. Arranged in the pump casing, between the two internal gear wheel pumps, is a partition wall, which separates the two internal gear wheel pumps spatially by its thickness and hydraulically. The partition wall can be interpreted as part of the pump casing. Open sides of the cup-shaped casing halves face one another, and end pieces of the casing halves form end walls of the pump casing and close off the pump casing from the outside at the ends. The end pieces or end walls have central holes, in which the pump shaft is rotatably mounted.

Another double internal gear wheel pump of this kind is disclosed by German Offenlegungsschrift DE 100 53 991 A1. This double internal gear wheel pump, too, has a multi-part pump casing comprising two cup-shaped casing halves, in which the two internal gear wheel pumps are accommodated. Open ends of the cup-shaped casing halves face one another and, arranged between them, is a partition wall, against the faces of which the casing halves rest. For connection, the casing halves surround a circumference of the partition wall with an encircling bead. The double internal gear wheel pump together with the pump casing thereof is inserted as a pump insert into a hydraulic block of a hydraulic vehicle brake system, which interconnects the double internal gear wheel pump as hydraulic or return pumps hydraulically to other hydraulic components of a slip control system of the vehicle brake system. Examples of such components are solenoid valves, check valves, hydraulic accumulators and dampers. The hydraulic block is connected to a brake master cylinder, and wheel brake cylinders are connected to the hydraulic block.

DISCLOSURE OF THE INVENTION

In the double internal gear wheel pump according to the invention, having the features in claim 1, the partition wall is an integral part of the pump casing. The pump casing is preferably open at both ends and closed by means of removable casing covers or other components, allowing the internal gear wheel pumps to be installed in the casing from the ends. One advantage of the invention is that there is no need for sealing between the partition wall and the pump casing, that there are no sealing problems at this point and that the partition wall cannot tilt in the pump casing during assembly because the partition wall is not fitted but is an integral part of the pump casing. Passing pump ports, i.e. pump inlets and outlets, through the partition wall is made simpler, there are no transitions for the pump ports from the pump casing to the partition wall, which transitions would require sealing, and the possibility that the pump ports in the pump casing will not communicate with the associated pump ports in the partition wall owing to incorrect mounting of the partition wall is excluded.

The term “internal gear wheel pump” in the sense according to the invention includes not only a “crescent pump” but also an “annular gear pump”, although this enumeration is not exhaustive.

The dependent claims relate to advantageous embodiments and developments of the invention indicated in claim 1.

The double internal gear wheel pump is preferably arranged in a hydraulic block of a hydraulic, slip-controlled vehicle brake system, which block forms the pump casing (claim 2). The hydraulic block interconnects the double internal gear wheel pump hydraulically to other hydraulic components of the slip control system of the vehicle brake system, such as solenoid valves, check valves, hydraulic accumulators, hydraulic dampers and pressure sensors. The hydraulic block is connected to a brake master cylinder, and wheel brakes of the vehicle brake system are connected to the hydraulic block. The two internal gear wheel pumps of the double internal gear wheel pump are separated from one another hydraulically, and each of the two internal gear wheel pumps is associated with one brake circuit of the vehicle brake system. The internal gear wheel pumps are hydraulic pumps and are also referred to as return pumps in slip-controlled vehicle brake systems.

Claim 3 envisages that the two internal gear wheel pumps of the double internal gear wheel pump according to the invention are crescent pumps, the crescents of which have a common abutment, which passes through the partition wall. By way of example, the abutment can be a pin which passes through the partition wall and on which the crescents are held in a pivotable manner. The crescents are bodies or, more generally, components which are arranged in a pump space of the internal gear wheel pumps which extends in a circumferential direction from a pump inlet to a pump outlet, between a ring gear and a pinion of the internal gear wheel pumps. Tooth tips of the pinion and of the ring gear slide on an inner and an outer side of the crescents, thereby enclosing volumes between the teeth of the pinion and of the ring gear, these volumes being pumped from the pump inlet to the pump outlet by rotary driving of the pinion and of the ring gear. Owing to its shape, the body is generally referred to as a crescent. However, it is not absolutely essential to the invention that the crescents be crescent-shaped. One abutment for both crescents of the two internal gear wheel pumps means that one less component, namely an abutment, is required and, in particular, that the outlay on assembly is reduced accordingly.

If pump ports, namely at least one pump inlet and/or one pump outlet, are passed through the partition wall, this being the subject matter of claim 4, any pump valves can be inserted into the respective pump port in the partition wall from the respective end of the pump casing before the internal gear wheel pump is installed in the pump casing. One possible example of such a pump valve is a check valve, which prevents any return flow of brake fluid through the internal gear wheel pumps counter to the direction of delivery when the internal gear wheel pumps are stationary. Such pump valves can be accommodated in a space-saving manner in the partition wall of the pump casing.

Claim 5 envisages that a shaft bearing of the pump shaft also simultaneously forms a motor bearing for a drive motor of the double internal gear wheel pump according to the invention. In particular, the drive motor is an electric motor. In this way, it is possible to eliminate one bearing, and centering of the drive motor and of the double internal gear wheel pump is ensured by means of the common bearing. The drive motor and the double internal gear wheel pump can have a common shaft which, in this case, forms both the pump shaft and the motor shaft. It is also possible for the drive motor to have a dedicated motor shaft.

BRIEF DESCRIPTION OF THE DRAWING

The invention is explained in greater detail below with reference to an embodiment illustrated in the drawing, in which:

FIG. 1 shows an axial section of a double internal gear wheel pump according to the invention;

FIG. 2 shows an end view of an internal gear wheel pump of the double internal gear wheel pump in FIG. 1; and

FIG. 3 shows an angled axial section of a pump casing of the double internal gear wheel pump in FIG. 1; the section plane is indicated by the line III-III in FIG. 2.

EMBODIMENT OF THE INVENTION

The double internal gear wheel pump 1 according to the invention, which is illustrated in FIG. 1, has two internal gear wheel pumps 2, 2′, which are arranged coaxially and with an axial spacing from one another on a common pump shaft 3. The internal gear wheel pumps 2, 2′ have pinions 4, 4′, which are fixed against relative rotation on the pump shaft 3 and mesh with a ring gear 5, 5′ at one point or over a region of their circumference. The pinions 4, 4′ are gear wheels, while the ring gears 5, 5′ are gear wheels with internal toothing. In FIG. 2, one of the internal gear wheel pumps 2 is shown in end view without a pump casing 6. The pump casing 6 has two cylindrical countersinks 7, 7′, in which the two internal gear wheel pumps 2, 2′ are accommodated and the ring gears 5, 5′ thereof can rotate. The countersinks 7, 7′ are axially parallel to the pump shaft 3 and are eccentric with respect to the pump shaft 3 in accordance with an eccentricity of the internal gear wheel pumps 2, 2′. The pump casing 6 is integral and has a partition wall 8, which is an integral part of the pump casing 6. The partition wall 8 is situated between the two internal gear wheel pumps 2, 2′ and separates them spatially from one another. The partition wall 8 has a through hole 9, through which the pump shaft 3 is passed. The pump shaft 3 is rotatably mounted in the partition wall 8 by means of a bearing bush 10. A sealing ring 11 provides a seal between the partition wall 8 and the pump shaft 3, ensuring that the two internal gear wheel pumps 2, 2′ are separated from one another hydraulically.

Arranged in a pump space 12 (see FIG. 2) of both internal gear wheel pumps 2, 2′ is a crescent 13, 13′, on the outside of which tooth tips of teeth of the ring gear 5 and on the inside of which tooth tips of teeth of the pinion 4 rest or along which they slide during operation. The crescent 13, 13′ is present in both internal gear wheel pumps 2, 2′. It encloses volumes between the teeth of the ring gear 5 and of the pinion 4 in order to bring about fluid delivery from a pump inlet 14 to a pump outlet 15 when the pinion 4, 4′ and, via the latter, the ring gear 5, 5′ are driven in rotation. The pump space 12 in which the crescent 13, 13′ is situated extends in the circumferential direction between the pinion 4 and the ring gear 5, from the pump inlet 14 to the pump outlet 15. The crescents 13, 13′ of the two internal gear wheel pumps 2, 2′ are held pivotably on a pin 16, which forms a common abutment or a common holder for the two crescents 13, 13′. The pin 16 is arranged axially parallel to the pump shaft 3 and passes through a bore in the partition wall 8. A sealing ring 17 seals off the pin 16 in the partition wall 8 of the pump casing 6.

The two countersinks 7, 7′ of the pump casing 6, in which the internal gear wheel pumps 2, 2′ are arranged, are closed by means of casing covers 18, 18′, which are pressed in in the illustrative embodiment shown, although this is not absolutely essential to the invention. The pump shaft 3 passes through one of the two casing covers 18, and it simultaneously forms a motor shaft of an electric drive motor (not shown). The pump shaft 3 is rotatably mounted in this casing cover 18 by means of a shaft bearing 19, a ball bearing in the illustrated embodiment of the invention. The shaft bearing 19 projects by about half of its width out of the casing cover 18, with the result that the electric drive motor (not shown) can be placed on and is centered relative to the double internal gear wheel pump 1 by means of the shaft bearing 19.

Pump ports, namely the pump inlets 14 and the pump outlets 15, are passed through the partition wall 8 of the pump casing. FIG. 3 shows an angled axial section of the pump casing 6 without the internal gear wheel pumps 2, 2′, with the section planes being chosen so that they pass through the pump inlet 14 and the pump outlet 15 of one internal gear wheel pump 2. The pump inlet 14 and the pump outlet 15 are embodied as angled bores which enter radially from the outside and exit radially outward and, after a bend through 90°, open axially parallel into the countersink 7 of the pump casing 6 in which the internal gear wheel pump 2 is arranged. The pump inlet and the pump outlet of the other internal gear wheel pump 2′ is offset in the circumferential direction by somewhat more than the diameter of the axially parallel part of the pump inlet 14 and of the pump outlet 15, with the result that the pump inlets 14 and pump outlets 15 of the two internal gear wheel pumps 2, 2′ are separated. The pump inlet and the pump outlet of internal gear wheel pump 2′ is therefore not visible in the drawing. Pump valves can be inserted into the pump ports 14, 15. Pump valves are valves of essentially any desired type associated with the internal gear wheel pump 2, 2′, which control a direction of flow through the internal gear wheel pumps, for example. Pressure-limiting or other valves are also possible as pump valves. In the illustrated embodiment of the invention, a check valve 18 is inserted as a pump valve into the pump outlet 15. The check valve 18 is inserted into the bore forming the pump outlet 15 in the partition wall 8 of the pump casing 6 before the installation of the internal gear wheel pump 2, 2′. In the same way, a valve can be inserted into the pump inlet 14, even if it is not provided in the embodiment.

In the illustrated embodiment of the invention, the pump casing 6 is formed by a hydraulic block of a hydraulic vehicle brake system, the rest of which is not illustrated. In addition to the two internal gear wheel pumps 2, 2′, other hydraulic components, such as solenoid valves, hydraulic accumulators, hydraulic dampers, check valves and pressure sensors (not shown) are inserted into the hydraulic block and interconnected hydraulically by bores. The internal gear wheel pumps 2, 2′ form hydraulic pumps of a slip control system of the hydraulic vehicle brake system (not shown). Such hydraulic pumps are also referred to as return pumps. The abbreviations ABS, ASR, ESP and/or FDR are customary for slip control systems. The hydraulic block is connected to a brake master cylinder, and wheel brake cylinders of the hydraulic vehicle brake system are connected to the hydraulic block. 

1. A double internal gear wheel pump, comprising: two internal gear wheel pumps having a common pump shaft: a pump casing; and a partition wall arranged in the pump casing between the two internal gear wheel pumps wherein the partition wall is an integral part of the pump casing.
 2. The double internal gear wheel pump as claimed in claim 1, wherein the pump casing is formed by a hydraulic block of a hydraulic vehicle brake system, the block interconnecting the internal gear wheel pumps hydraulically with other hydraulic components of the vehicle brake system.
 3. The double internal gear wheel pump as claimed in claim 1, wherein the two internal gear wheel pumps have crescents with a common abutment passing through the partition wall.
 4. The double internal gear wheel pump as claimed in claim 1, wherein a pump port passes through the partition wall and opens into one of the internal gear wheel pumps, and wherein a pump valve is inserted into the pump port.
 5. The double internal gear wheel pump as claimed in claim 1, wherein the pump shaft has a shaft bearing simultaneously forming a motor bearing for a drive motor of the double internal gear wheel pump. 